Assembly for the blades of variable pitch airscrews



Manin 9, 194s.

ASSEMBLY FOR P. P. RATIE ErAL -2,313,301 THE BLADES OF VARIABLE FITCHAIRSCREWS Filed Feb. 14, 1940 .IL 4 F' Flai 5, 7"'5? Hag 2. f a? F7 7lFa `P E INVENTQ s' PIERRE PAUL, R RsN JEAN yRM1 RATlfgli;

Patented Mar. 9, 1943 a n v2,313,301 y c ASSEMBLY non 'rnc ananas orVARIABLE FITCH SCREWS Pierre Paul Rati and Ren .lean Rati, Montrouge,France; vested in theA Alien Property Custodian Application ren-nary 1e,1940, senti No. 318,888

In France February 28; 1939 The present invention has for object anassemn bly for the blades of variable pitch airscrews. This assembly,which can be used for metal or wooden blades, is more particularlyapplicable to wooden blades; it improves the securing in position andthe safety ci the blades whilst allowing the latter to be rapidlyassembled and replaced (a)` The root of eachl blade is engaged, parlticularly by screwing, in a socket rotatively' mounted in thecorresponding radial drum of the alrscrew hub.

(b) The socket is preferably slotted and provided withlocking meansensuring the locking of the rigid connection between the root andthesocket, the putting out of action of the locking means allowing theblade to be dismantled whereioisliihe socket remains in position on theairscrew (c) The socket is hem axially in the drum, in

Lillie centrifugal direction, by a ball bearing or the (diA The socketis held laterallyin the drumfby a ring, preferably a conical ring,pressing against' initially be made to the diagrams 2 Claims. (Cl. 17u-162) given with reference to the accompanying draw Fig. .3 is a partialelevation, in section, of ,an v

assembly devised according to the invention. y

In order to indicate ,the technical advantages obtained by the -assemblyforming the subjectmatter of the present application, reference will xillustrated in Figs'. 1 and 2. 1

Fig. 1 shows a rod I subjected, `on the one hand, to the 'action of atransverse force F1 and, on the other hand, to the action of alongitudinal force F5. ,The force F1 presses the rod I against a bearing2, the reaction on an abutment 3, parallel to the bearing 2, being F1.Bycomposing F1 and F3 a reaction Fz is obtained on the bearing 2 whichis equal to the sum of F1 and F2 and which gives, in absolute value,th'e value of the shearing being equal' to the force F5' a correspondingbearing of the drum, said ring being keyed on the socket.

(e) `The ring is preferably made of a phenolic plastic known as Celeron.

(f) Resiliently distortable' means, such as a washer or a resilienttube, are interposed between the conical ring and the member locking thesocket on the root of the blade, said means acting,

with a certain amount of pressure, on the ring and on the ball'bearing.

(y) The shearing stress is supported by the ring whereas the centrifugalstress and the bending stresses are exerted on the ball abutment whichsurrounds the socket and has, for that purpose, a large diameter, thering pressed against the conical bearing of the drum acting moreover asa brake and as a shock absorber for the blades mainly in order to avoidhammering on the members controlling the incidence of the blades. 1

The invention also includes other particular stress exerted on'the rodI; Moreover, said rod I is secured at 6 to the `abutment 3, the reactionFfi Fig. 2 shows a rod i which, as the previous rod, is subjected to theaction of both force F1 and Fi.v In the case of Fig. 2, said rod Icomprises transverse part I-I" pressed against abutments 8 and f 9. Saidrod I is pressed against the bearing 2 by the force F1 and the reactionon the bearing 2 is f 1i"I which is only equal to F1. In fact, in saidFigure 2, the abutment 3 parallel to thebearing 2 (Fig. 1) is replacedby the two abutments 8 and Sat right anglesuto said bearing. In theseconditions, the reactions on the abutments 8 and 9, o' the forces F1 andF5, are indicated by F8 and F9, a part of the reaction F being due tothe force F1`only.

If vthe rod I diagrammatically illustrates an airscrew blade subjected,on the one hand, to bending stresses F1 owing to the pull exerted bysaid blade during its utilisation and, on the other hand, to centrifugalforce F5, it will be seen that, in the case of the assembly of Fig. 2,the shear ing stress exerted on the embedding of the ',root (bearing 2)is considerably reduced in the case of Fig. 2 relatively to a bladevmounted as illustrated by the diagram of Fig. 1. Fig. 3 illustrates' anassembly carrying into practice the diagram of Fig. 2. The'root I of a4blade is screwed in a socket, I0 provided withl a flange I I and cut atI2 so as to constitute-a worm vwheel meshing ywith a worm I4controllingv the variation of the pitch of the blades. A ball bearing 8,surrounding the socket f I 0,- is `interpbsecl points which will appearln the following textos between the aange Il and a shoulder l5 formedconical bearing I9 lock-nut 30.

on a corresponding radial drum I6 rigid with the hub I 8 of theairscrew. i

The socket Ill, which is held in the centrifugal direction by the ballbearing 8, is radially retained by a ring 2 made of a phenolic plasticsuch as Celoron for instance, said ring 2 being pressed by its outerconical surface against a corresponding allowing an assembler to rigidlyand positively .provided 'at the en(d of the lock saidvsocket and thecorresponding root of` the blade after saidroot has been screwed in thesocket'. 'I'hese locking means are constituted by a slotted ring orcollar screwed on the `corre lsponding end, also slotted. of the socketIII. ,After engaging a resilient tube 2 |taking a bearling on the ring2, the collar 20 isscrewed on the socket III to a distance suicient fortensioningthe ring 2 I to the desired amount and ahbolt or the like isengaged in lugs 22 of the collar`20 to lock the latter in position andrigidly lock the socket III-and the root l of the blade.

The ring2 isrendered angularly rigid with the socket I0 by a key 2",fluid-tight packings being provided at 24 and 25.1 A fluid-tight plateis also provided at 26 lbetween the ball bearing 8 `and the shoulder I5of the. d rum I8. The various drums each receiving a blade form part ofone and the same member which is `locked in position on the hub I8through the medium of. a conical ring 28 and a nut 29 combined with a Itwill also be noted that the end of the root I n of the blade is providedwith a metal annular edge 3l, held in position by screws 32 and which iscentered in a corresponding bearing 33 of the socket I0. Y

' According to an important feature of the presvent invention, the rootI of each blade is mounted, in an easily removable mannenin thecorresponding socket i l0 which is' permanently and rotatively mountedin the corresponding drum I6 of the hub. In fact, the assembly or thetaking to pieces of each blade necessitates solely the lscrewing orunscrewing of the blade after putting out of action the locking meansconstituted by the collar-20 and without it being necessary to dismantlethe mechanism controlling the variation of the pitch of the blades.

It will be noted that the ball bearing 8 acts as the abutment. 8-9 ofFig. 2. The centrifugal stress of the blade is exerted on the ballbearing 8. Moreover, owing to the large diameter of said ball bearings,the bending stresses of the blade .are also exerted on said ballbearing. The shearing stress is exerted .on the conical ring 2 made ofthe phenolic plastic Celoron which constitutes, furthermore, a frictionmember forming shock absorber for the 'blades mainly in-order to avoidhammering on the members controlling the incidence ofthe blades. Theresilient tube 2| exerts a certain amount of pressure on the conicalring 2 and on the ball bearing 8. The centrifugal force exerted on theblades pressing against the bearing 8 prevents bending movement. 'I'heresilient tube 2| ensures acertain tension at low working speed and atrest. This metal tube compensates the reduction of centrifugal force forholding each blade in a correct position notwithstanding the action,even refV` duced, of the bending stresses.

It is obvious that the embodiment described` and illustrated is givenherein only by way of indication and not in a limiting sense. Allmodifications or changes which do not alter in any way the main featuresabove set forth or the desired result, remain included in the scope ofthe present invention.

What we claim as our invention and desire to secure by Letters Patentis:

1. Inv al variable pitch airscrew -having a plu-I ralityof drums orfixed sockets extending radi- -ally from a hub mounted on a drive shaft,means for retaining the root of each blade of the airscrew in assembledassociation with its respective 'drum on said hub, said means includinga socket member secured to the root of each bladel `and mounted forrotation in one of said drums, a bearing disposed on each drum or fixedsocket and a ring which is preferably of conical form engaging againsteach drum bearing and serving to retain the respectively associatedsocket member, a disengageable locking member which serves to lock therespective root of a blade in each socket member, a resilientlydeformable annular member interposed between said locking member and-theconical ring and a ball bearing surrounding each socket member so as tofacilitate rota said -ring and said ball bearing.

- 2. In a variable pitch airscrew having a plurality of drums or fixedsockets extending radially from a hub mounted on a drive shaft,` meansfor retaining the rootof each blade of the airscrew in assembledassociation with its respective drum on said hub, said means including asocket member secured to the root of each blade and mounted for rotationin one of said drums, a bearing disposed on each drum or fixed socketanda ring which is preferably of conical form engaging against each drumbearing and serving to retain the `respectively associated socketmember, a disengageable locking member which serves to-` lock therespective root of a blade in each socket member, a ballibearing oflarge diameter surrounding each socket member so as to facilitaterotation and cooperate in retaining the same REN JEAN RATI.

